Advances in seed science and site-specific farming have shown that crop yields can be increased in certain situations by planting a field with two or more varieties of seed rather than planting the entire field with only one variety. Differences within one field such as soil type, elevation, moisture, weed pressure and/or pests can make it beneficial to plant different seed varieties in different locations within a field. The use of global positioning information enables machines to be controlled based on location within the field.
While different areas within a field can be distinguished with a bright line, it is difficult to make a sudden change in seed type without some blending of seed variety over a considerable distance in the field. One device that makes a clear transition in seed types is disclosed in U.S. Pat. No. 6,845,724. There, a planter row unit 25 is shown having two seed meters 26. A transition in seed types can be made suddenly, with no blending, by turning off one meter and turning on the other meter. What is not shown, however, is how to feed seed from two meters into a single seed furrow using a single furrow opener, seed tube and furrow closing mechanism. Feeding a single seed tube with seed from one of two meters and maintaining seed spacing accuracy is a challenge.